1. Field of the Invention
The present invention relates to a pen such as a ball-point pen, a correction pen, or a glue pen, and more particularly to a pressurized pen enabling smooth supply of medium such as ink, correction fluid, or glue at the time of using the pen.
2. Description of the Related Art
Conventional pens such as ball-point pens have the disadvantage in that a pen tip must be rubbed several times on a paper whenever the ink doesn't smoothly come out of a pen tip of a pen refill unit at the time of using the pen, or the ink is exhausted in the course of writing down on notes.
In this regard, as disclosed in the JP 2005-280119 A, a knock-type ball-point pen is known, in which a press pump mechanism formed of a cylinder and a piston is disposed in a pen refill unit of the pen, a loop-shaped elastic ring made for example of rubber is disposed on a front end portion of the piston that is in sliding contact with an inner peripheral surface of the cylinder, and the press pump mechanism is interlocked with a knock mechanism, a compression chamber in the cylinder is compressed by a knocking operation of the piston at the time of using the pen, and an inside of an ink containing tube filled with ink is pressurized.
In the knock-type pen disclosed in above mentioned publication, the outer peripheral surface of the loop-shaped elastic ring in the front end portion of the piston is brought in close contact with the inner peripheral surface of the cylinder and thus isolated from the outside air, and the piston is moved frontward in cooperation with the knock mechanism at the time of using the pen, whereby air in the compression chamber within the cylinder is pressurized. However, when fabricating the loop-shaped elastic ring, outer diameter precision of the loop-shaped elastic ring may be lowered by irregularities of the outer diameter or burrs caused by joint lines of a mold, and thus the case where the sealing ability is not sufficient occasionally occurs.
To increase the sealing ability by minimizing deformation of the loop-shaped elastic ring, it is necessary to employ a large design value of the outer diameter of the loop-shaped elastic ring.
Meanwhile, when the large design value of the outer diameter of the loop-shaped elastic ring is employed, it is required to use a spring having a high elastic coefficient in order to decompress the piston to its original position of the rear.
Then, conversely, there is a problem of deteriorating the feeling of using the pen since the large force is needed to perform the knocking operation at the time of using the pen.